There are known systems for whitening teeth using toothpaste with abrasives for removing extrinsic stains.
There are likewise known systems for whitening teeth using hydrogen peroxide.
There is a known attempt to whiten teeth using ultrasound by means of mechanical removal of extrinsic stains.
As further background, the following discussion regarding tooth structure and known whitening methods is provided.
Tooth enamel is predominately formed from an inorganic substance, hydroxyapatite crystals, along with approximately 5% organic materials, predominantly collagen. The dentin is composed of about 20% protein including collagen; the balance of inorganic materials including hydroxyapatite crystals. The acquired pellicle is a proteinaceous layer on the surface of tooth enamel, and that may be removed after an intensive tooth cleaning.
Tooth stains are generally classified as either extrinsic or intrinsic, depending on whether the stain is on the surface of the tooth within the acquired pellicle or within the tooth structure itself within the enamel or dentin. For example, extrinsic staining of the acquired pellicle can occur from foods or compounds, which contain tannins and other polyphenolic compounds which become trapped in the lightly bound proteinaceous layer on the surfaces of the teeth. Extrinsic tooth staining is removed by mechanical methods, such as by using abrasives applied by a toothbrush by a user on his or her teeth, or by a dental professional blasting a patient's teeth with an abrasive. A problem with these methods is that the consumer experiences minimal initial and longterm tooth whitening (e.g., 6 months).
Intrinsic staining, on the other hand, occurs when chromogens and pre-chromogens penetrate the enamel and dentin and become tightly bound to the tooth structure. Intrinsic staining can occur when blood or amalgam products leach into the enamel and dentin. Intrinsic staining likewise can occur systemically from excess fluoride intake during enamel development leading to a mottled yellow or brown stain of fluoresce staining. Intrinsic staining is not removable by mechanical methods of tooth cleaning and generally requires the use of chemicals, for example strong oxidizing agents such as hydrogen peroxide which can penetrate into the tooth structure to effect a change in the light absorbtivity of the stain chromogen and/or the solubility of the chromogens.
The desire for whiter, lighter teeth is considered to be cosmetic and desirable in today's cosmetically-orientated society. Tooth bleaching is generally accomplished by gels, pastes, or liquids which contain an oxidizing agent such as hydrogen peroxide (H2O2) that attack (i.e., chemically react with) the chromogen molecules, making them colorless and/or water soluble, making the tooth appear lighter and brighter, thus resulting in lighter brighter teeth.
The most commonly used oxidizing agent is hydrogen peroxide (H2O2), such as from carbamide peroxide (CH6N2O3), which is mixed with an anhydrous viscous carrier containing glycerin, known as glycerol (C3H8O3) and/or propylene glycol and/or polyethylene glycol (C3H8O2). Sodium chlorite, chlorine dioxide, peracetic acid or ethaneperoxoic acid (C2H4O3) may likewise be used as an oxidizing agent.
When in contact with water, carbamide peroxide dissociates into urea, also known as carbamide (CH4N2O) and hydrogen peroxide (H2O2). The hydrogen peroxide in the presence of water then dissociates into water and oxygen anions. It is these oxygen anions which react with the stain making them more water soluble, transparent, or both.
There are several known delivery systems to deliver carbamide peroxide, for example, to the surfaces of the teeth.
A common approach is to have a dental professional construct a custom-made tray from an impression of the patient's teeth. An oxidizing gel is dispensed into the tray by the patient and the tray is worn over the teeth intermittently for a period of days to several weeks, depending on the severity of the staining. This approach has been known to cause tooth sensitivity in over 60% of the users, and it can be uncomfortable for the users to wear the tooth bleaching trays. Tooth sensitivity is believed to result from the movement of fluid through the dentinal tubules, which is sensed by nerve endings within the tooth. The carriers, glycerin propylene glycol and polyethylene glycol, draw fluids toward them and therefore contribute to the tooth sensitivity often experienced by wearing a bleaching tray.
Another known approach is to incorporate an oxidizing agent in a strip and have the patient wear the strip intermittently over a period of two weeks. This approach also has had the disadvantage of being awkward for users to wear, and many users also experience tooth sensitivity. Further, the known strips have an inherent problem of contacting the teeth only on the facial surfaces and fail to remove the staining which occurs in between the teeth in the interproximal areas.
Other known methods of intrinsic whitening include applying the whitening compound directly on the user's teeth which is easy for the user to apply but still takes several days to achieve desired results.
It can thus be seen that there is a need for a more effective and even faster tooth whitening device and method that provide enhanced tooth whitening results.
There are known tooth whitening devices, methods, and compositions that use heat and light to accelerate the tooth whitening chemical reactions. Another known method of intrinsic whitening is using non-heat light energy to activate a photo initiator in the whitening solution therefore accelerating the whitening result.
As used herein, sonochemistry relates to the effect of ultrasonic waves on chemical reactions. Chemical effects of ultrasound arise from changes, such as acoustically induced cavitation and induced temperature rises in a composition, rather than from a direct interaction with a molecule in question. It is that enhancement of a chemical reaction which is used to synergistically enhance the chemical effect on the whitening of teeth in the present invention. See, e.g., Practical Sonochemistry Power Ultrasound Uses and Applications Mason, Timothy J. et al., Hoorwood, 2nd Ed., 2003, ISBN: 978-1-898563-83-9.